1. Field of the Invention
The present invention relates to a cutting tool shrink fitting method and to a cutting tool obtained by this method.
2. Discussion of the Background
FIG. 6 shows a conventional example of a cutting tool fitting method of this type.
This cutting tool 1 is equipped with a tool holding portion 3 and a tool 2. The tool holding portion 3 is configured to be attached to the spindle of a machine tool (not shown). The tool 2 is shrink fitted into the tool holding portion 3.
The tool holding portion 3 includes a tapered arbor 4, a grip 5, and a support portion 7. The tapered arbor 4 is configured to be secured, for example, to the spindle of the machine tool. The grip 5 in the form of a disc has a diameter larger than that of the arbor 4. Further, the grip 5 has a machine tool. The grip 5 in the form of a disc has a diameter larger than that of the arbor 4. Further, the grip 5 has a groove portion to be gripped by a tool replacing arm or the like. The support portion 7 has, for example, a tapered configuration and a substantially cylindrical hole 6 at the center. The arbor 4, the grip 5 and the support portion 7 are formed coaxially and as an integral unit to have a central axis (O) for rotation. The hole 6 of the support portion 7 is equipped with a cylindrical inner peripheral surface 8 having an inner diameter (d) and a bottom surface 9 positioned at the deepest end of the hole 6. A large diameter groove (8a) is coaxially formed in the inner peripheral surface 8.
Only the cylindrical shaft portion at the base end side of the tool 2, which is shrink fitted into the hole 6 of the tool holding portion 3, is shown. This tool 2 has an outer diameter (D) which is somewhat larger than the inner diameter (d) of the hole 6, and the difference between this outer diameter (D) and the inner diameter (d) of the hole 6, (Dxe2x88x92d), is the interference.
The shrink fitting method for this cutting tool 1 will be described. First, as shown in FIG. 6, the base end surface (2a) of the tool 2 is placed on the end surface (7a) on the hole opening (6a) side of the tool holding portion 3. The tool 2 is positioned substantially coaxially with the hole 6. This state is a positioning state at a room temperature. An operator maintains the tool 2 in this state manually or by using a jig. Next, the support portion 7 of the tool holding portion 3, which has the hole 6, is heated so that it thermally expands. When the inner diameter (d) has become larger than the outer diameter (D) of the tool 2, the tool 2 is pressed into the hole 6 to fit into the hole 6.
When the hole portion 6 has contracted by cooling, the tool 2 and the tool holding portion 3 are centered with each other and secured each other by the interference pressure.
However, in this cutting tool 1, at the time of positioning prior to the shrink fitting, it is necessary that the operator hold the tool 2 by hand or a jig such that the base end surface (2a) of the tool 2 abuts the end surface 7a where the hole 6 of the tool holding portion 3 opens. Accordingly, the operation was complicated. Furthermore, the hole 6 and the tool 2 must be positioned coaxially at the time of positioning the tool 2 before the tool 2 can be efficiently inserted at the time of heating.
According to one aspect of the invention, a cutting tool shrink fitting method includes inserting a guide portion which is coaxially connected to a tool main body of a tool into a hole formed in a tool holding portion. A shoulder portion which connects the tool main body and the guide portion sits on a surface around the hole of the tool holding portion in order to position the tool with respect to the tool holding portion. The tool holding portion is heated such that the tool main body of the tool is inserted into the hole. Then, the tool holding portion is cooled.
According to another aspect of the invention, a cutting tool includes a tool holding portion and a tool. The tool holding portion includes a hole having a hole inner diameter. The tool is configured to be inserted into the hole of the tool holding portion. The tool includes a tool main body, a guide portion and a shoulder portion. The tool main body has a tool outer diameter larger than the hole inner diameter of the hole when the tool holding portion is not heated. The guide portion is coaxially connected to the tool main body and configured to position the tool substantially coaxially with respect to the tool holding portion. The guide portion has a guide outer diameter smaller than the hole inner diameter of the hole so that the guide portion is inserted into the hole. The shoulder portion is formed between the tool main body and the guide portion so as to sit on a surface around the hole to support the cool when the guide portion is inserted into the hole.
Further, according to the other aspect of the invention, a cutting tool shrink fitting method includes inserting a guide portion which is coaxially connected to a tool main body of a tool into a hole formed in a tool holding portion in order to support and position the tool substantially coaxially with respect to the tool holding portion such that a shoulder portion which connects the tool main body and the guide portion sits on a surface around the hole of the tool holding portion. The tool holding portion is heated such that the tool main body of the tool is inserted into the hole. The tool holding portion is cooled.